植物TIR-NB-LRR类型抗病基因各结构域的研究进展

植物抗病反应是一个多基因调控的复杂过程,在这个过程中R基因发挥了非常重要的作用。根据其氨基酸基序组成以及跨膜结构域的不同,R基因可以分为多种类型,其中NBS-LRR类型是植物基因组中最大的基因家族之一。TIR-NB-LRR类型的抗病基因又是NB-LRR类型中的一大类,也是目前抗病基因研究的热点。该文总结了TIR-NB-LRR类型抗病基因各个结构域的功能和相关的研究进展。相关研究表明,TIR结构域主要通过自身或异源的二聚体化介导抗性信号的转导,但也有部分研究表明,该结构域可能参与病原菌的特异性识别。NBS结构域常被认为具有"分子开关"的功能,它可以通过结合ADP或ATP来调节植物抗病蛋白的构象变化,从而调节下游抗病信号的传导。LRR结构域在植物与病原菌互作的过程中可以通过与病原菌的无毒蛋白直接或间接互作来特异识别病原菌。也有研究发现,LRR结构域具有调节信号传导的功能。这些信息将为研究植物抗病机理提供理论依据,也为将来通过基因编辑技术对作物进行定向抗病育种提供思路。     

Hedyotis koiana R. J. Wang,a new species of Rubiaceae from China

Hedyotis koiana R. J. Wang is described as a new species from Guangdong, Hunan, Jiangxi, Guangxi, Fujian, and Hainan provinces of China. It is most similar to H. herbacea L. and H. pinifolia Wall. ex G. Don. because they all have narrow leaves and their capsules are loculicidally dehiscent at the top, but it differs from H. herbacea by having termi- nal or upper axillary cyme and narrow leaves, and it can be distinguished from H. pinifolia by having long flowering pedicles, sparse inflorescence, and adaxially glabrous corolla.     

RXLR-mediated entry of Phytophthora sojae effector Avr1b into soybean cells does not require pathogen-encoded machinery

Effector proteins secreted by oomycete and fungal pathogens have been inferred to enter host cells, where they interact with host resistance gene products. Using the effector protein Avr1b of Phytophthora sojae, an oomycete pathogen of soybean (Glycine max), we show that a pair of sequence motifs, RXLR and dEER, plus surrounding sequences, are both necessary and sufficient to deliver the protein into plant cells. Particle bombardment experiments demonstrate that these motifs function in the absence of the pathogen, indicating that no additional pathogen-encoded machinery is required for effector protein entry into host cells. Furthermore, fusion of the Avr1b RXLR-dEER domain to green fluorescent protein (GFP) allows GFP to enter soybean root cells autonomously. The conclusion that RXLR and dEER serve to transduce oomycete effectors into host cells indicates that the >370 RXLR-dEER-containing proteins encoded in the genome sequence of P. sojae are candidate effectors. We further show that the RXLR and dEER motifs can be replaced by the closely related erythrocyte targeting signals found in effector proteins of Plasmodium, the protozoan that causes malaria in humans. Mutational analysis of the RXLR motif shows that the required residues are very similar in the motifs of Plasmodium and Phytophthora. Thus, the machinery of the hosts (soybean and human) targeted by the effectors may be very ancient.     

Synthesis of caged 2,3,3a,7a-tetrahydro-3,6-methanobenzofuran-7(6H)-ones: Evaluating the minimum structure for apoptosis induction by gambogic acid

We have reported the discovery of gambogic acid (GA) as a potent apoptosis inducer and the identification of transferrin receptor as its molecular target. In order to understand the basic pharmacophore of GA for inducing apoptosis and to discover novel and simplified derivatives as potential anti-cancer agents, we explored the synthesis of caged 2,3,3a,7a-tetrahydro-3,6-methanobenzofuran-7(6H)-ones (4-oxatricyclo[4.3.1.0]decan-2-ones). Three types of 2,3,3a,7a-tetrahydro-3,6-methanobenzofuran-7(6H)-ones based on xanthone, 2-phenylchromene-4-one and benzophenone, were synthesized using a Claisen/Diels-Alder reaction cascade. All the reactions produced the targeted caged compound as well as its neo-isomer. The caged compounds based on xanthone and 2-phenylchromene-4-one were found to maintain the apoptosis inducing and cell growth inhibiting activity of GA, although with less potency. The caged compounds based on benzophenone were found to be inactive. Our study determined the minimum structure of GA for its apoptosis inducing activity, which could lead to the development of simple derivatives as potential anti-cancer drugs.     

小鼠胸腺髓质上皮细胞系体内诱导胸腺细胞功能成熟

来源于BALB/c小鼠 (H-2^d)胸腺的髓质上皮细胞系MTEC1细胞表达H-2^d和I -A^d 分子 .为研究上皮细胞诱导胸腺细胞阳性选择及功能分化的能力 ,首先用γ 线照射C5 7BL/6J小鼠(H-2^d) ,再经静脉注射 (H-2^b×d)F1代骨髓细胞 ,制备 H-2^b×d→H-2^b)嵌合体 ,然后将MTEC1细胞注射到嵌合体胸腺内 .注射后 2个月 ,经HE染色显示 ,MTEC1细胞在嵌合体小鼠胸腺被膜下皮质区成簇存在 ,体外免疫学试验发现 ,嵌合体小鼠脾细胞含有抗原特异性H-2^d识别限制的杀伤T细胞 (CTL) ,IL -2产生T细胞及增殖应答T细胞 .在MLR试验中 ,嵌合体小鼠脾细胞显示对H-2^d 同种异型抗原的明显耐受 .从而证明MTEC1髓质上皮细胞能在胸腺微环境内诱导H-2^d识别限制的对特异抗原应答的T细胞发育及功能成熟 .由此提出在胸腺髓质区进行“2次胸腺选择”的假说 ,并讨论了其意义 .     

美引烤烟品种NC102品质特征分析

通过对美引烤烟品种NC102、红花大金元和K326的化学成分、致香成分和感官评吸比较分析,进一步明晰了NC102的品质特征.NC102品种烤烟在石油醚提取物总量及新植二烯含量上具有明显优势,清甜香气风格突出,与K326比,在香气的细腻度、圆润性、飘逸感方面优于K326品种,在叶组配方中可以用作次主料使用.